“My job has recently been transferred from the UK to an Asian country. With the move from my established position to a new challenging role in a new environment, I suddenly found myself lacking my usual level of confidence...”

If you have any accent other than a standard British one,
the chances are that option 2 and option 3 will strengthen your native accent
taking you further away from a British accent. As you may know by now, A
British accent resonates largely in the back of the mouth, around the soft
palate and in the torso. Most other accents resonate much more in the mouth. So
we will be focusing on diaphragmatic breathing.

Your diaphragm is located just below the ribcage, as
indicted in the photo, below:

The diaphragm is a large dome shaped muscle located just
below the lungs where the two sides of the ribcage meet. Technically, it
contracts when we breathe in filling the lungs, but you will feel a sense of
expansion in this area as the air fills the space just above the diaphragm. It
is this sense of expansion that will help you to use your diaphragm.

Exercise: Lie down on a flat surface (floor or bed), place
your hand just in between the two sides of the ribcage, and breathe in deeply.
Maintaining the expansion created in this area, say a short phrase or sentence.
As you run out of breath, you will feel the area mentioned contracting, simply
pause and take in another breath. With practice, you will be able to use your
diaphragm by just thinking about it. Wherever you focus goes, your voice will
travel.